How does an FMU work???
 

Do you have to use an FMU with a blower?? I am new to the supercharger world and trying to get as much info before I install it. I have one with the blower I got but its calibrated for 19# injectors, and I have 30's..What is the purpose of an FMU?? I know it has to do with fuel but exactly what does it do??

FMU's are a quick and dirty fix for supplying extra fuel to the system via a reference to boost pressure to raise fuel pressure in porportion.

As for not using an FMU. At least in a mass air car, the injectors and the mass air need to be sized correctly so that you don't exceed the 4.99 volt window trying to feed fuel to the engine.